The present invention relates to a vehicle motion stability control apparatus, and particularly relates to an apparatus for controlling at least one of braking force and driving force applied to a vehicle, to stabilize a motion thereof.
In order to improve a stability of a vehicle, there is known heretofore a vehicle motion control apparatus for stabilizing a yawing motion of the vehicle. As an example of the apparatus, a vehicle dynamics control (VDC) system for maintaining a stability of a vehicle in a lateral direction thereof is explained in pages 668-677 of a book entitled AUTOMOTIVE HANDBOOK published by Robert Bosch GmbH, in October, 1996. That system is explained as the one that prevents the vehicle “pushing out” of the turn or spinning out of the turn when it is steered, and it is a closed-loop (feedback) control system integrated within the vehicle's brake system and powertrain. It describes how the vehicle is to behave at the physical driving limit in accordance with a driver's input, and how it actually behaves, and describes that in order to minimize the difference between nominal and actual behavior (deviation), the tire forces are controlled by actuators, and the VDC controller is controlled, with slip angle and yaw rate provided for the state variable.
U.S. Pat. No. 6,263,261 discloses a roll control system for use in a vehicle that is not dependent upon the turning condition of the vehicle. And, it discloses a plurality of sensors sensing the dynamic conditions of the vehicle and including a speed sensor, a lateral acceleration sensor, a roll rate sensor, and a yaw rate sensor are coupled to a controller, which determines a roll angle estimate in response to lateral acceleration, roll rate, vehicle speed, and yaw rate, and which determines a brake pressure distribution in response to the relative roll angle estimate.
Also, Japanese Patent Laid-open Publication No.11-304663 and its English abstract of esp@cenet database, discloses a device to rationally estimate the behavior of a vehicle such as a skid and a wheel lift by real-time operation, and to estimate the height of center of gravity. It is described in the English abstract that the transfer function of roll for the steering angle of a dynamics model with degree of freedom including the roll is equal to that of the roll for the steering angle being obtained by the AR method (auto-regressive method) from data being sampled from a loaded vehicle, thus deriving the height of center of gravity by comparing coefficients.
In order to ensure the stability for the yawing motion and rolling motion of the vehicle, it is required to combine the apparatus for stabilizing the yawing motion of the vehicle (yawing motion stability control apparatus) as described in the aforementioned book, and the apparatus for stabilizing the rolling motion of the vehicle (rolling motion stability control apparatus) as described in the aforementioned United States Patent. Supposing that those apparatuses are combined together, signals of the sensors commonly required by those apparatuses can be used commonly. However, with respect to the apparatus for stabilizing the yawing motion, for example, such a new sensor for detecting the rolling motion as a roll velocity sensor (roll rate sensor) or the like is required. In addition, as a roll increasing tendency in the rolling motion of the vehicle varies in dependence on loading conditions or the number of passengers, it is also required to detect a height of the center of gravity of the vehicle or the like, thereby to determine the roll increasing tendency during cornering operation of the vehicle properly. In the aforementioned Japanese Patent Laid-open Publication, the roll rate sensor has been used for estimating the height of the center of gravity.